One construction of a prior art radial support bearing assembly for supporting a camshaft includes a cage, an outer race, and a plurality of needle roller elements. Additionally, an inner race can also be provided so that the inner raceway for the needle roller elements is not directly on the outer surface of the camshaft. Typically, the support bearing assembly is positioned within a corresponding cylinder head and the cylinder head maintains the support bearing assembly in a predetermined position, coaxial with the camshaft. As such, the support bearing assembly provides a low friction support mechanism for allowing the camshaft to rotate in place (e.g., within the cylinder head of an internal combustion engine).
By definition, the outer race of the bearing assembly is clamped in the cylinder head and does not rotate with the camshaft. The needle roller elements contact the outer surface of the camshaft (when a separate inner race is not provided) and experience rolling engagement therewith. The clamping of the outer race in the block provides some resistance to axial movement of the outer race, but does not guarantee the proper alignment with the rolling elements. Therefore, the initial installation of the support bearing assembly in the block is complicated by the lack of any means for positively axially positioning the radial bearing assembly relative to either the block or the camshaft.
Additional issues arise in many prior art radial support bearing assemblies in those instances in which the distance along the camshaft between adjacent cam lobes is substantially greater than the axial length of the cage of the bearing. More specifically, in these instances, it is possible that the cage and, therefore, needle roller elements move axially along the camshaft relative to the outer race of the bearing. Mispositioning of the needle roller elements can lead to imbalanced loads, increased wear, reduced roller life, etc. To alleviate these issues, prior art bearing assemblies exist in which the axial length of the cage is increased to match the distance between adjacent cam lobes. However, when cage length is increased without similar length increases in the needle rollers, dynamic behavior of the bearing can be affected. As well, increasing the axial length of the cage, and possibly rollers, may lead to increased manufacturing costs due to the use of extra material and the need for more accurate tolerances.
The present invention recognizes and addresses considerations of prior art constructions and methods.